A Novel Rotation Mechanism of F1-ATPase Based on the Water-Entropy Effect

Abstract

We propose a novel picture of the rotation mechanism of F1-ATPase [1]. In the proposal, the key factor is the translational entropy of water, which has been shown to drive a variety of self-assembly processes in biological systems [2]. We calculate the hydration entropies of three different sub-complexes comprising the gamma subunit, one of the beta subunits, and two alpha subunits adjacent to them. The calculation is made using the angle-dependent integral equation theory combined with the multipolar water model [3] and morphometric approach [4]. The major finding is that the packing in F1-ATPase is highly asymmetrical and this asymmetry is ascribed to the water-entropy effect. We discuss how the rotation of the gamma subunit is induced by such chemical processes as ATP binding, ATP hydrolysis, and release of the products. In our picture, the asymmetrical packing plays crucially important roles and the rotation is driven by the water-entropy effect. As part of the demonstration of the validity of our rotation mechanism, we also analyze the water-entropy change in yeast F1-ATPase during 16-degree rotation of the gamma subunit [5]. The result demonstrates the validity of the water-entropy mechanism proposed in Ref 1.[1] T. Yoshidome, Y. Ito, M. Ikeguchi, and M. Kinoshita, J. Am. Chem. Soc. 133, 4030 (2011).[2] M. Kinoshita, Front. Biosci. 14, 3419 (2009).[3] M. Kinoshita, J. Chem. Phys. 128, 024507 (2008).[4] R. Roth, Y. Harano, and M. Kinoshita, Phys. Rev. Lett. 97, 078101 (2006).[5] T. Yoshidome, Y. Ito, N. Matubayasi, M. Ikeguchi, and M. Kinoshita, Soft Matter (to be submitted).